The present invention relates to agglomeration of comestible materials.
Particulate comestible materials commonly are agglomerated to adjust the bulk density, appearance and other properties of the product. Typically, water soluble particulate materials such as soluble or "instant" coffee are agglomerated by exposing the particles to a vigorous jet of steam. The steam condenses on the particles, moistening and heating them so that each particle is covered with a sticky flowable coating of soft, wet material. When the coated particles contact one another in the turbulent environment created by the jet, the particles adhere to one another and the coatings on the contiguous particles merge, thereby joining the particles into agglomerates. Upon drying, the merged coatings solidify and form welds between adjacent particles in each agglomerate.
Processes of this nature typically produce agglomerates having smooth, rounded edges and a spongy texture. In the case of soluble coffee, the agglomerates ordinarily have a uniform dark color.
Such agglomerates do not look like roast and ground coffee. Roast and ground coffee ordinarily incorporates particles of various shapes including some sharp-edged granular particles, having various colors ranging from light tan to dark brown. Soluble coffees made by freeze-drying processes which do not involve agglomeration typically incorporate sharp-edged particles. Consumers tend to associate the appearance of roast and ground coffee and the appearance of freeze-dried coffee with flavor quality. Accordingly, there has been a need for improved control of particle shape and color in agglomeration of soluble coffee to provide agglomerated products resembling roast and ground coffee or freeze-dried coffee. There has also been need for improvement in control of product bulk density. There have been corresponding needs in agglomeration of other comestible materials such as tea, chicory, cocoa and the like.
The steam jet agglomeration process typically requires large quantities of steam for each unit of product to achieve satisfactory fusion between the particles. High steam consumption imposes a significant cost. Moreover, exposure of the particles to the steam typically causes appreciable loss of fugitive flavor constituents, and this effect ordinarily is related directly to the amount of steam applied. There has accordingly been a need for agglomeration processes and apparatus which alleviate these drawbacks.